Implantable leads having electrodes are used in a variety of applications, including the delivery of electrical stimulation to surrounding tissue, neural or otherwise, as well as measuring electrical energy produced by such tissue. Some leads include lumens for the delivery of other elements, including chemicals and drugs. Whether in a stimulation, sensing or element delivery capacity, such leads are commonly implanted along peripheral nerves, within the epidural or intrathecal space of the spinal column, and around the heart, brain, or other organs or tissue of a patient.
Differing techniques have been utilized to construct or manufacture such leads. Some prior art leads and methods of manufacture have been disclosed in several United States patents, such as U.S. Pat. Nos. 5,016,646 (Gotthardt, et al.), 5,433,742 (Willis), 6,208,881 (Champeau) and 6,216,045 (Black, et al.), which are each incorporated herein by reference. One example of a directional brain stimulation and recording leads is disclosed in PCT publication WO 02/045795 (Jun. 13, 2002), which is incorporated herein by reference. A length of tubing having a window cut therein forms a sleeve insulating member (or formed by injection molding, vulcanization molding) that is placed over the distal end of the lead.
Generally, several elements (conductors, electrodes and insulation) are combined to produce a lead body. A lead typically includes one or more conductors extending the length of the lead body from a distal end to a proximal end of the lead. The conductors electrically connect one or more electrodes at the distal end to one or more connectors at the proximal end of the lead. The electrodes are designed to form an electrical connection or stimulus point with tissue or organs. Lead connectors (sometimes referred to as contacts, or contact electrodes) are adapted to electrically and mechanically connect leads to implantable pulse generators or RF receivers (stimulation sources), or other medical devices. An insulating material typically forms the lead body and surrounds the conductors for electrical isolation between the conductors and protection from the external contact and compatibility with a body.
Such leads are typically implanted into a body at an insertion site and extend from the implant site to the stimulation site (area of placement of the electrodes). The implant site is typically a subcutaneous pocket that receives and houses the pulse generator or receiver (providing a stimulation source). The implant site is usually positioned a distance away from the stimulation site, such as near the buttocks or other place in the torso area. In some cases, the implant site (and/or insertion site) is located in the lower back area, and the lead may extend through the epidural space (or other space) in the spine to the stimulation site (middle or upper back, or neck or brain areas). In other cases, the implant site may be located in the brain or other part of the body. In still other cases, the stimulation source may not be implanted, and may be external to the body.
Application of specific electrical fields to spinal nerve roots, spinal cord, deep brain stimulation, and other nerve bundles or tissue for the purpose of pain control has been actively practiced for years. While a precise understanding of the interaction between the applied electrical energy and the stimulated tissue is not fully appreciated, it is known that application of an electrical field to spinal or other tissue (e.g., spinal nerve roots and spinal cord bundles) can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated tissue.
It is known that each exterior region, or each dermatome, of the human body is associated with a particular spinal nerve root at a particular longitudinal spinal position. The head and neck regions are associated with C2-C8, the back regions with C2-S3, the central diaphragm is associated with spinal nerve roots between C3 and C5, the upper extremities correspond to C5 and T1, the thoracic wall extends from T1 to T11, the peripheral diaphragm is between T6 and T11, the abdominal wall is associated with T6-L1, the lower extremities related to L2 to S2, and the perineum from L4 to S4. By example, to address pain sensations that commonly focus on the lower back and lower extremities, a specific energy field can usually be applied to a region between bony level T8 to T10. As should be understood, successful therapy management and the avoidance of stimulation in unafflicted regions generally requires the applied electric field to be properly positioned longitudinally along the dorsal column.
Therapy-managing electrical energy is commonly delivered through electrodes positioned at the desired stimulation site. The electrodes are generally carried by one of two types of leads: percutaneous and laminotomy (commonly referred to as “paddle” leads).
Percutaneous leads (including catheter types) are generally small in diameter and have a plurality of spaced electrodes. Percutaneous leads are typically placed within the body through the use of a Touhy-like needle. For insertion, the Touhy-like needle is passed through the skin at the desired location (insertion site) and the lead is inserted through the needle.
Laminotomy leads have a paddle configuration, and are generally larger than percutaneous leads, and typically possess a plurality of electrodes (for example, two, four, eight, or sixteen) arranged in one or more columns.
Laminotomy leads are generally used for applications in which is it desirous that the applied electrical energy (stimulation) be directional in nature, such as to address both unilateral and bilateral pain, where electrical energy may be administered using either column independently (on either side of the midline) or administered using both columns to create an electric field which traverses the midline. A multi-column laminotomy lead may enable reliable positioning of a plurality of electrodes, and in particular, provide a plurality of electrode columns that do not readily deviate from an initial implantation position/orientation.
However, laminotomy leads require a significant surgical procedure for implantation. The surgical procedure generally requires the resection and removal of certain tissue (vertebral tissue in the case of spinal applications) to allow both access to the dura and proper positioning of a laminotomy lead.
Percutaneous leads, in contrast, require a less-invasive implantation method, and with a plurality of electrodes, provide a user the ability to create almost any electrode array. However, prior art percutaneous leads generally have band-type electrodes whereby the electrical energy field radiates circumferentially and therefore the electrical energy may not be focused solely on the desired area. Although likely more stable during use and directional in nature, laminotomy leads require a more complicated surgical procedure for implantation and removal.
Notwithstanding the range of electric fields that are possible with conventional stimulation leads, in certain instances it is necessary to concentrate electrical energy at a particular point, or over a small region. As an example of such occasion, assume therapy-managing electrical energy is applied at or about T8 to address only localized lower back pain. At T8, spinal nervous tissue corresponding to the patient's lower extremities may also commingle with the specific spinal nervous tissue associated with the lower back. Since it is common that the lower back-related spinal nervous tissue is deeply embedded within the combined spinal nervous tissue, it becomes desirable to focus applied electrical energy to the targeted nervous tissue to (i) reach the deeply situated target nervous tissue and (ii) avoid undesirable stimulation of unafflicted regions, while avoiding surgical procedures for the lead(s) implantation and removal.
Accordingly, a need exists for a stimulation lead that includes a structural arrangement that facilitates directional concentration of delivered electrical energy at a point, i.e., for a given electrode, or over a small region, i.e., for a plurality of electrodes, and at the same time, may be implanted (and/or removed) without significant surgical procedure.
Additionally, implantation of leads using percutaneous methods involves the insertion of the lead into the body via a needle used as a passageway into the body. During the insertion procedure, the lead is pushed (forward) into the body, and in some occasions, there is a need for the lead to be pulled back (partly or completely) through the needle. This problem is described further by reference to FIG. 10. FIG. 10 illustrates the lead or catheter being inserted through the needle, and the potential problem when the lead is pulled back through the needle, likely due to repositioning by the clinician. When this occurs with prior art needles, there is a likelihood that the needle will cut or damage the lead, as shown.
Accordingly, there exists a need for a needle for use in percutaneous insertions which reduces the likelihood that, when an inserted lead is pulled back through the needle, the lead could be damaged.